A theoretical insight into the catalytic effect of a mixed-metal oxide at the nanometer level: The case of the highly active metal/CeOx/TiO2(110) catalysts

The structural and electronic properties of CeOx species supported on the rutile TiO2 110 surface have been examined by means of periodic density-functional calculations that use a generalized gradient approximation functional including a Hubbard-like type correction. Deposition of Ce atoms leads in a first step to Ce3+ ions bound to the surface through bridge and in-plane oxygen atoms, the released electrons occupying the Ti 3d empty orbitals. Further addition of Ce and molecular oxygen gives place to Ce2O3 dimers diagonally arranged on the surface, in agreement with the spots observed in the scanning tunnel microscope images. The formation process of CeOx nanoparticles NPs on the TiO2 surface is highly exothermic and our calculations show that the redox properties of the Ce III-Ce IV couple are significantly altered when it is supported on TiO2. In particular the reactivity against CO/O2 indicates that on the surface the presence of Ce III is favored over Ce IV species. Our results also indicate that the CeOx /TiO2 interface should be seen like a real mixed-metal oxide rather than a supported NP of ceria. Finally, in the context of the high catalytic activity of the M /CeOx /TiO2 M =Au,Cu,Pt systems in the water-gas shift reaction, we have examined the dissociation of water on the CeOx /TiO2 surface and estimated a barrier as small as 0.04 eV, i.e. 8 times smaller than that computed for a TiO2 oxygen vacancy. This result agrees with the experimental superior catalytic activity of the M /CeOx /TiO2 systems over M /TiO2.Gobierno de España. Ministerio Ciencia e Innovación (MICINN) MAT2005-01872 y CSD2008-0023Junta de Andalucía FQM-132Departamento de Energía de EE. UU. División de Subvención de Ciencias Químicas DE-AC02-98CH1088

Interaction of oxygen with TiN (001): N↔O exchange and oxidation process

This work presents a detailed experimental and theoretical study of the oxidation of TiN(001) using a combination of synchrotron-based photoemission and density functional theory (DFT). Experimentally, the adsorption of O2 on TiN(001) was investigated at temperatures between 250 and 450K. At the lowest temperature, there was chemisorption of oxygen (O2,gas→2Oads) without significant surface oxidation. In contrast, at 450K the amount of O2 adsorbed increased continuously, there was no evidence for an oxygen saturation coverage, a clear signal in the Ti 2p core level spectra denoted the presence of TiOx species, and desorption of both N2 and NO was detected. The DFT calculations show that the adsorption/dissociation of O2 is highly exothermic on a TiN(001) substrate and is carried out mainly by the Ti centers. A high oxygen coverage (larger than 0.5 ML) may induce some structural reconstructions of the surface. The exchange of a surface N atom by an O adatom is a highly endothermic process (ΔE=2.84eV). However, the overall oxidation of the surface layer is thermodynamically favored due to the energy released by the dissociative adsorption of O2 and the formation of N2 or NO. Both experimental and theoretical results lead to conclude that a TiN+mO2→TiOx+NO reaction is an important exit channel for nitrogen in the oxidation process.Ministerio de Educación y Ciencia de España, MEC. MAT2005-01872Junta de Andalucía. FQM-132División de Ciencias Químicas del Departamento de Energía de EE. UU. DE-AC02-98CH10086Fundación japonesa para la Ciencia de los Materiale

Sibling competition and not maternal allocation drives differential offspring feeding in a sexually size-dimorphic bird

Sex allocation models still fail to predict the complex sex ratio patterns in broods of vertebrates. A major problem when studying mother–brood interactions is the difficulty in disentangling hypotheses involving maternal preferences from processes that do not imply maternal manipulation. We studied maternal resource allocation in mixed-sex, same-sex and single-chick broods in the great bustard, Otis tarda. Females normally rear a single chick, and previous work has shown that maternal investment influences male more than female breeding success. Therefore, mothers of two-chick broods were assumed to be in good condition and candidates to show a preference for sons. Results showed that male chicks of mixed-sex broods remained close to the mother for twice as long as their sisters, and received double the number of maternal feedings. However, sex differences in maternal feeding rate disappeared when considering only simultaneous begging approaches from both siblings. Proximity to the mother and its interaction with begging approach intensity were the factors determining the higher begging success of male chicks. In single-chick broods, females did not receive fewer maternal feedings than males. Overall, our results suggest that female chicks of mixed-sex broods become outcompeted by their larger brothers, which remain close to the mother much longer, preventing their sisters from taking a larger share of maternal feedings. We conclude that mothers do not show a preference for feeding male over female chicks, and that the sex differences in feeding rate are determined by the higher food requirements of male chicks due to their sexually selected, much faster growth rates. The higher mortality of females in mixed-sex broods contrasts with the pattern of male-biased mortality typical in this species, and supports our interpretation of an asymmetric competitive ability of male offspring as the mechanism responsible for the sex bias in maternal expenditure.This work was supported by the Dirección General de Investigación Científica y Técnica (projects PB91-0081 and PB94-0068, with contributions from other projects awarded to J.C.A. for marking and radiotracking birds 1987–2013); the Instituto Nacional para la Conservación de la Naturaleza; and the Junta de Castilla y León. During the study, E.M. benefitted from a predoctoral fellowship of the Dirección General de Investigación Científica y Técnica. Research by J.C.A. and J.A.A. was supported by project CGL2012-36345 during the writing of the pape

Migration Patterns in Male Great Bustards (Otis tarda)

5 paginas, 1 figura y 1 tableThe Great Bustard (Otis tarda) is distributed from Iberia and Morocco in the west to China in the east and has been considered sedentary in all but the northern and eastern parts of its range (Gewalt 1959, Glutz et al. 1973, Cramp and Simmons 1980). However, some studies have reported seasonal changes in population numbers in different areas in the Iberian Peninsula (Hidalgo and Carranza 1990, Alonso et al. 1995), suggesting that the species is a partial migrant (sensu Terrill and Able 1988) in this region. We describe seasonal movements of marked adult male Great Bustards and discuss observed patterns in relation to the following questions: (1) Do migratory males display interannual fidelity to breeding and postbreeding areas? (2) Do males travel significantly farther than females in their seasonal movements? We also suggest several hypotheses that could explain patterns of partial and differential migration in male Great Bustards.This study is a contribution to DGICYT-project PB94–0068.Peer reviewe

Evaluation of captive breeding as a method to conserve threatened Great Bustard populations.

6 paginas y 1 tableThe recent Great Bustard Action Plan summarizes de main recommended lines of action to preserve current populations and their habitats in Europe. Among others, captive breeding is mentioned as a method to save clutches found in the field whose hatching success probability is suspected to be low for any reason. Birds hatched from these clutches have been used to either build up small captive-breeding flocks that ensure preservation of the genetic pool of seriously threatened populations once these may be extinct, or to be released into the natural populations as juveniles. In this paper we evaluate the viability of captive breeding in the light of new results of a recent study of juvenile Great Bustards during their maternal dependence period, family break-up and dispersal. The few data available on survival of captive-bred young after being released suggest that they suffer a high mortality, probably due to the lack of the experience acquired in natural conditions from their mothers. The negative effects of imprinting by their human keepers, particularly in relation with display and mating, has not been sufficiently investigated. These and other aspects make captive breeding questionable as an effective method, as compared with habitat protection measures.PB94-0068 of the Dirección General de Investigacion Cientifica y TecnicaPeer reviewe

Cardiovascular disease versus periodontal disease: chronic systemic infection as a link

Objective : Analysis of the alleged connection between the periodontal and cardiovascular disease, with reference to periodontal pathogens as a risk factor for heart disease. Researching method : A research was carried out at Medline/Pubmed. Included criteria and researching strategy. The articles selection has been made taking into account key-terms appearing either in the title or in the summary. Experimental studies in animals, clinical prospective studies performed with a minimum sample size (>30) and studies written in English have been included. The rejected criteria were the following: clinical retrospective studies and/or studies carried out with a low sample size (n<30). Results : Within systemic diseases related to periodontal ones, the alleged link between periodontal and heart and circulatory disease has been one of the most investigated in recent times. Different authors consider the existence of a link between the diseases as such, inappropriate and implausible since both the diseases have risk factors in common (age, gender, smoking, diet, oral hygiene and diabetes). However, speculations about the origin of the diseases were raised when it was demonstrated that some bacteria species, bacteria proteins and lipopolysaccharide are present at the plaques of atherosclerosis that obstruct the coronary arteries. The mechanisms of this connection have been analyzed following an actualized review. Conclusion : Most of the experimental and clinical studies ensure that a positive association between periodontal disease and heart disease has been found, once the con-founder factors have been eliminate

Migration Patterns in Male Great Bustards (Otis tarda)

5 paginas, 1 figura y 1 tableThe Great Bustard (Otis tarda) is distributed from Iberia and Morocco in the west to China in the east and has been considered sedentary in all but the northern and eastern parts of its range (Gewalt 1959, Glutz et al. 1973, Cramp and Simmons 1980). However, some studies have reported seasonal changes in population numbers in different areas in the Iberian Peninsula (Hidalgo and Carranza 1990, Alonso et al. 1995), suggesting that the species is a partial migrant (sensu Terrill and Able 1988) in this region. We describe seasonal movements of marked adult male Great Bustards and discuss observed patterns in relation to the following questions: (1) Do migratory males display interannual fidelity to breeding and postbreeding areas? (2) Do males travel significantly farther than females in their seasonal movements? We also suggest several hypotheses that could explain patterns of partial and differential migration in male Great Bustards.This study is a contribution to DGICYT-project PB94–0068.Peer reviewe

Impact of regulation fair disclosure on corporate communications with investors

In this study we report laser ablation–inductively coupled plasma–mass spectrometer U-Pb ages of granitoids from the so-called early granodiorites of the northwest Iberian Variscan belt. The U-Pb results attest to significant magmatic activity in Visean time (ca. 347–337 Ma) that generated a hitherto poorly constrained granitoid suite in the northwest Iberian tract of the western European Variscan belt realm. This early Carboniferous suite (ECS) is mainly composed of peraluminous cold and hot crustal granodiorites and monzogranites with minor associated mafic rocks that attest to minor involvement of mantle melting. Based on the geochronological and geochemical data, we compare the Visean granitoids with younger Variscan granitoids in northwest Iberia and, in view of the tectonothermal scenarios of the Variscan collision in northwest Iberia, propose a model for the genesis of the ECS in northwest Iberia that involves rapid melting upon fast exhumation of the thickened Gondwanan crust in the course of the protracted Variscan collision.This work has been funded by the Spanish Ministry of Economy and Competitiveness under the project ODRE III—Oroclines & Delamination: Relations & Effects (CGL2013-46061-P) and Происхождение, металлогения, климатические эффекты и цикличность Крупных Изверженных Провинций (КИП) (Origin, metallogeny, climatic effects, and cyclical large igneous provinces) (14.Y26.31.0012; Russian Federation) to Gutiérrez-Alonso and López-Carmona and CGL-2016-76438-P to Fernández-Suárez. López-Carmona was also funded by a “Juan de la Cierva” grant (reference FJCI-2014-20740).Peer reviewe

Cu Deposited on CeOx-Modified TiO2(110): Synergistic Effects at the Metal-Oxide Interface and the Mechanism of the WGS Reaction

Experimental techniques and DFT calculations have been combined to study and compare the effect of the metal-substrate interaction in Cu/TiO2(110) and Cu/CeOx/TiO2(110) catalysts for the water-gas shift (WGS) reaction. Experiments and theory show that CeOx nanoparticles affect the dispersion of copper on titania, and on the formed copper-ceria interface, there are synergistic effects which favor water dissociation and the WGS reaction. The minimum energy path for the WGS reaction on the new highly active catalytic system Cu/CeOx/TiO2(110) has been predicted by theoretical calculations. Main steps such as adsorption-dissociation of water and∗OCOH carboxyl intermediate formation-deprotonation have been characterized. In this very particular system, water splitting is no longer the rate-limiting step because it can dissociate overcoming an energy barrier of only 0.92 kcal/mol. One important insight of the present work is to show that easy full hydration of the ceria particles strongly lowers the reaction barrier for the deprotonation of the∗OCOH intermediate and facilitates the evolution of the WGS reaction. For the first time, a system has been found on which the WGS reaction is able to work with all the involved energy barriers below 12 kcal/mol. This remarkable behavior makes the metal/CeOx/TiO2 family a potential candidate for industrial application as catalysts in the WGS reaction. The change in the metal-support interactions when going from Cu/TiO2 to Cu/CeOx/TiO2 illustrates the importance of optimizing the oxide phase when improving the performance of metal/oxide catalysts for the WGS.Ministerio de Economía y Competitividad MAT2012-31526, CSD2008-0023U.S. Department of Energy DE-SC001270